Variable-ratio drive for electronic line



April 4, 1961 c. E. DORAN 2,978,536

VARIABLE-RATIO DRIVE FOR ELECTRONIC LINE SCAN AND RECORDING MACHINES 2 Sheets-Sheet 1 Filed June 9, 1958 INVENTOR.

ATTORNEY Apnl 4, 1961 c. DORAN 2, 8,5 6

VARIABLE-RATIO DRIVE FOR ELECTRONIC LINE SCAN AND RECORDING MACHINES Filed June 9, 1958 2 Sheets-Sheet 2 INYENTOR. /MQL E3 5. .DOQAN, BY

ATTORNE Y 2,978,536 i 'Iatented Apr. 4, 1 961 VARIABLE-RATIO DRIVE FOR ELECTRONIC LINE SCAN AND RECORDING MACHINES Charles E. Doran, Wantagh, N.Y., assignor to Fairchild Camera and Instrument Corporation, a corporation of Delaware Filed June 9, 1958, Ser. No. 740,645 6 Claims. (Cl. 1786.6)

This invention pertains generally to an apparatus for the electrical reproduction of images, and more specifically to such an apparatus in which the reproduction may selectively be an enlargement or a reduction of the original image, and in a selectable ratio in either case.

While not limited thereto, the inventive concept of the present invention will be described in connection with the art of photoelectric engraving and recording machines. The particular type of photoelectric machine to which this invention is most applicable usually comprises a pair of rotary drums having a common source of motive power for achieving synchronous rotary motion of the two drums. One of the drums includes means for releasably securing thereto a sheet or the like which bears the image to be reproduced. Mounted adjacent this .drum or sliding motion parallel to the axis thereof is a photoelectric transducer which serves to scan the image and produce electrical signals corresponding to the image information. The other drum includes means for releasably securing thereto a sheet of recording material. Mounted adjacent this second drum for sliding motion parallel to the axis thereof is an output transducer which is electrically connected to the photoelectric pick-up transducer to receive signals therefrom and which serves to record the image on the recording sheet on the second drum. The nature of the recording device is a matter of choice, and may comprise a heated stylus for vertical relief engraving of the recording sheet, a source of light and a light valve for photographic reproduction, or any other suitable means.

In order to provide synchronous motion of the two transducers axially of the two drums, a common drive means for the transducers is connected to the aforemen tioned motive power source. This common drive means may conveniently take the form of an endless belt of some suitable relatively inextensiblc material such as steel, the belt being secured to the two transducers and passing over and extending between a pair of pulleys or wheels at least one of which is rotated by the motive source. Such an apparatus forms the subject matter of US. Reissue Patent Number Re. 23,914 to J. A. Boyajean and assigned to the assignee of the present invention. As disclosed in this prior patent, suitable means may be provided for inserting a screen signal in the information supplied to the output transducer whereby a half-tone reproduction is achieved.

As disclosed in the aforementioned patent, the apparatus is limited to a fixed size ratio between the copy or original image and the reproduction thereof, unless, for example, one of the drums and a drive wheel were replaced by similar parts of different size.

It is therefore a primary object of the present invention to provide an apparatus for the electrical reproduction of images wherein the size ratio between the original copy and the reproduction thereof is variable.

Another object of the invention is to provide an apparatus for the electrical reproduction of images wherein the degree of enlargement or reduction between the original copy and the reproduced image is smoothly and continuously variable between the limits of maximum enlargement and maximum-reduction.

An additional object of the invention is to provide an apparatus for the electrical reproduction of images wherein the degree of enlargement or reduction between the original copy and the reproduced image in two mutually orthogonal directions on the original copyis controlled by a single control means.

Still another object of the invention is to provide an apparatus for the electrical reproduction of images wherein the degree of enlargement or reduction between the original copy and the reproduced image in two mutually orthogonal directions on the original copy is controlled by a single control means, but wherein the degree of enlargement or reduction in one of said directions may differ from that in the other direction to a selectable degree.

In accordance with the present invention, the above and other objects are achieved by means of a pair of variableratio drive means which respectively interconnect the two drums and the two transducer means. A single motive power means is provided to produce rotary motion of one of the two drums and synchronous translatory motion of the transducer means associated with that drum. One of the variable-ratio drive means connects the second drum to the first drum to rotate the former at a speed selectably different from that of the latter. The other variable-ratio drive means connects the second transducer means to the drive mechanism for the first transducer means to effect translatory motion of the former at a speed selectably different from that of the latter.

The two variable-ratio drives are substantially identical, and each includes a first rotary input member of a differential mechanism and a rotary conical cam member both driven by gearing connected to the input of the particular variable-ratio drive means. One end of a reciprocally-mounted spring-loaded toothed rack member engages the cam surface of the cam member, and a pinion gear engages the toothed portion of the rack member. Secured to a common axle with the pinion gear is a second rotary input member of the differential mechanism, and the output member of the differential is connected by suitable gearing to the output of the par ticular variable-ratio drive means. Each of the cam members is mounted for reciprocal motion along its rotary axis, and means are provided for positioning each of the cams translationally in this direction to bring a selectable portion of the cam surface under the bearing end of the rack member. As the cam member is thus adjusted, the rack member the cam member) executes reciprocal excursions of varying amplitudes, and the pinion gear follows in corresponding rotary excursions. Since the first input of the difierential mechanism is constantly rotating, the variable excursion of the second input member (which is secured to the pinion gear) is transferred to the output member.

With the above considerations and objects in mind, the invention itself will now be described in connection with a preferred embodiment thereof given by way of example and not of limitation, and with reference to the accompanying drawings, in which:

Fig. l is a perspective view of the apparatus of the invention, showing the operative relationship between the several components thereof.

Fig. 2 is a plan view of the details of the variableratio drive means which interconnects the two transducer means in the apparatus of the invention.

Fig. 3 is a plan view of the details of the variable-ratio (upon simultaneous rotation of drive means which interconnects the two rotary drums in the apparatus of the invention.

Fig. 4 is an elevation of the control means for the variable-ratio drive means of Figs. 2 and 3.

Fig. 5 is a sectional view taken along line 5-5 in Fig. 4.

Fig. 6 is an elevation of a modification of certain of the elements shown in Fig. 4.

Referring now to Fig. 1, a pair of cylindrical drums 10 and 12 are shown with their respective axles 14 and 16 in substantial alignment. Drums 10 and 12 are mounted for rotation about their axles by means of bearings not shown. Each of the drums 10 and 12 includes means for releasably securing thereto a sheet of suitable material. In the case of drum 10, the sheet material to be held around the periphery of the drum is the original or copy material. The recording material is secured to the periphery of drum 12. Any suitable means for releasably securing such sheet material around the drums may be utilized, and one example of such means is the slotted portion 11 in each drum surface which allows the edges of the sheet material to pass toward the center of the drum to be gripped by means similar to those shown and described in the copending application to Reuben J. Autere et al., Serial Number 559,023, filed January 13, 1956, and assigned to the assignee of the present invention.

Two transducer assemblies 18 and 20 are shown adjacent drums 10 and 12, respectively, and each is mounted for linear reciprocal movement along guide bars 22 which are substantially parallel to axles 14 and 16. A motor 24, which may be of any suitable type, has an output shaft 26 with a worm 28 secured thereto. The worm 23 engages worm gear 30 which is secured to a continuation of shaft 16. Thus when motor 24 is energized, shaft 16 is rotated continuously through worm 28 and worm gear 30. Also affixed to the continuation of shaft 16 is a worm 32 which engages and drives a worm gear 34 which is secured to a shaft common with worm 36. A worm gear 38 engages and is driven by worm 36, and is secured to a shaft to which is also affixed a pulley or drive wheel 40. An endless belt 42, which is preferably of some relatively inextensible material such as steel, passes over and extends between wheel 40 and a matching wheel 44. One of the reaches of belt 42 is secured to transducer assembly 20 as shown, so that the latter is pulled along rods 22 as wheel 40 is rotated.

A housing 46 encloses a pair of variable-ratio drive means which are not shown in this figure, but which will be described below in connection with subsequent figures of this specification. With respect to the description of Fig. 1, it will sufiice tostate that the variable-ratio drive means included within housing 46 serve respectively to connect axle 14 of drum 10 to axle 16 of drum 12, and the first of a second pair of drive wheels 48, 50 to drive wheel 44. The ratio of operative speed between the input and output elements of the devices included within housing 46 is controlled by the setting of control knob 52, in a manner to be described.

Passing over and extending between wheels 48 and 50 is a second endless belt 54, one of the reaches of which is secured to photoelecrtic pick-up transducer means 18 so as to pull the latter along bars 22 as drive wheel 43 is rotated.

-.ith the exception of the variable-ratio drive means included within housing 46, the structure so far described herein is for the most part closely similar to the apparatus forming the subject matter of the aforementioned Boyajean patent, and the operation thereof, aside from the variable-ratio drive function, is substantially that of the Boyaiean apparatus. The electrical circuitry is shown in an abbreviated schematic form herein, mostly to indicate the fact of electrical continuity between the photoelectric pick-up transducer 18 and the recording or reproducing transducer 20 through amplifier 56. The details of such circuitry are shown and described in the Boyajean patent, and further description in this specification will not be had since such circuitry forms only an incidental part of the invention herein disclosed.

Fig. 2 shows in detail the variable-ratio drive means which connect transducer assemblies 18 and 20 together and which is included in housing 46. Wheel 44, which is rotatably driven by endless belt member 42, and spur gear 58 are secured to a common shaft so that the two rotate together. Spur gear 60 engages spur gear 58 and is secured to a shaft 62 which has secured thereto a bevel gear 64 and a spur gear 66. Bevel gear 64 forms one of the rotary input members of a differential mechanism indicated generally at 68, and to which further reference will be made below. Spur gear is affixed to a shaft 72 and engages an idler gear 74 which in turn is engaged by spur gear 66. The diameters of wheel 44 and gears 58, 60, 66 and 70 are so interrelated as to effect one complete revolution of shaft 72 during the time taken for belt 42 to pull transducer assembly 20 along rods 22 the distance of one complete scan along the length of drum 12.

A rotary conical cam member 76 is keyed to shaft 72 as at 78 for rotation therewith and for sliding axial motion relative thereto. Secured to one end of cam member 76 is a retaining means 80 including a slotted or recessed portion 82 which receives an end of an adjusting bracket 84 which will be described in more detail in connection with Fig. 4. It will be seen that as the bracket 84 (shown in Fig. 4) moves axially of shaft 72, cam member 76 is drawn along the shaft with the retaining means 80. Due to the cone-like shape of cam member 76, axial movement of the cam in a direction away from gear 70 causes the near end of rack 85 to bear against portions of the cam surface which represent progressively smaller cam radii.

Rack 85 is mounted for reciprocal motion in the direction of its length, and is spring-loaded as by resilient means 86 constantly to urge the rack toward the right in Fig. 2 in order to ensure that the rack follows the earn as the latter is either rotated or moved along its shaft 72. Teeth 88 on rack member 85 engage a pinion gear 90, so that as the rack is reciprocated pinion gear 90 is rotated. Pinion 90 is affixed to a shaft 92 which extends into dif' ferential mechanism 68 to provide the second rotary input to that mechanism. As may be seen, shaft 92 is forked within the differential mechanism, the axial fork merely serving to position this end of the shaft in rotary bearing 94. The other two forks have bevel gears 96 and 98 mounted thereon for rotary motion relative to the respective forks.

The fourth bevel gear of the differential 68 is indicated at 100, and this gear serves as the output of the differential, being secured to a hollow shaft 102 which is concentric with and which encompasses shaft 92. A second bevel gear 104 secured to shaft 102 engages an idler bevel gear 106, which in turn engages an output bevel gear 108. The latter gear is affixed to a hollow shaft which is concentric with and which encompasses shaft 62. Wheel 48, which transmits the output motion to endless belt 54, is also secured to hollow shaft 110.

Fig. 3 shows in similar detail the variable-ratio drive means which interconnects the two rotary cylindrical drums 10 and 12. Afiixed to shaft 16 is a bevel gear 112 which engages a bevel gear 114 secured to shaft 116. Also secured to shaft 116 is a spur gear 118 and a bevel gear 120, the latter serving as one of the rotary inputs to a differential mechanism 122 later to be described. Spur gear 118 engages an idler gear 124, which in turn engages a spur gear 126 secured to a shaft 128. The diameters of gears 112, 114, and 126 are so interrelated as to cause one complete revolution of gear 126 for each rcvolution of drum 12.

A conical cam member 130 is keyed to shaft 128 as at 132 for rotary motion therewith and sliding motion rela.- tive thereto. Secured to one end of earn 130 is a retaining means 134 which includes a slotted or recessed portion 2,97a,5se

136 which receives an end of an adjusting bracket 84 which will be described in more detail in connection with Fig. 4. As was described in connection with cam member 76 shown in Fig. 2, as bracket 84 (shown in Fig. 4) moves axially of shaft 128, cam member 130 is drawn along the shaft with retaining means 134. Due to the cone-like shape of cam 130, axial movement of the cam in a direction away from gear 126 causes the near end of rack 13-8 to bear against portions of the cam surface which represent progressively smaller cam radii.

Rack 138 is mounted for reciprocal motion in the direction of its length, and is spring-loaded as by resilient means 140 so as to be urged constantly toward the right in Fig. 3 to follow the cam surface as different portions of the latter are presented. In both rack members 138 and 85, the end which bears against the respective cam surface may conveniently include a ball or roller bearing to reduce friction to a minimum. Teeth 142 on rack 138 engage a pinion gear 144 which is secured to a shaft 146, one end of which extends into differential mechanism 122 and which end serves as the second rotary input member to the differential mechanism. Within the differential 122. the shaft 146 is forked to present one axial fork which fits which into a bearing 147 for positioning of the shaft, and two transverse forks which have mounted thereon bevel gears 148 and 150 which are free for rotation relative to the respective forks. As may be seen, bevel gears 148 and 150 each engage bevel gear 120.

A fourth bevel gear 152 of differential mechanism 122 engages gears 148 and 150 and serves as the output member of the differential, being secured to a hollow shaft 154 which is concentric with and which encompasses shaft 146. Also affixed to hollow shaft 154 is a bevel gear 156 which engages an idler bevel gear 158, which in turn engages a double bevel gear 160. The latter engages a bevel gear 162 which is secured to shaft 14 of drum 10.

As shown in Fig. 4, the means for controlling the axial or translational positioning of the two cam members76 and 130 may conveniently comprise a single control knob 52 which serves to rotate the shaft 164 having a portion 166 which is threaded. Bracket 84 includes a suitable nut 168 which is engaged by the threads of shaft portion 166, and the ends of the bracket, which ends may as a matter of convenience be forked, reside in the slotted or recessed portions 82 and 136 of the retaining means 80 and 134, respectively. Thus, as knob 52 and shaft 164 are rotated, the relative turning of shaft portion 166 and nut 168 causes the latter and bracket 84 to advance along the shaft 164, carrying cams 76 and 130 therewith. It will be understood that the spur gears 70 and 126 are stationary with respect to axial movement along shafts 72 and 128, respectively, and do not move with the cams in the manner just described.

Fig. 5 is a sectional view taken on line 5-5 in Fig. 4, showing the general cross-sectional shape of the two cams 76 and 130 as Archimedean spirals, i.e., the plane curve generated by a point moving away from or toward a fixed point at a constant rate while the radius vector from the fixed point rotates at a constant rate. With such a crosssection for each of the cams, the amplitude of the throw or displacement of the respective rack members will bear a linear relationship to the amplitude of the rotation of the cams, which latter amplitude was stated previously to bear a one-to-one ratio to the rotation of the two cylindrical drums. Thus, while the drive effected between the two drums and between the two transducer assemblies is variable, linearity is maintained.

A variation in the structure of the bracket 84 is shown in Fig. 6, wherein'the bracket comprises two portions 84. Instead of the single nut shown in Fig. 4, each half of the bracket includes a half-nut 168. Since bracket members 84' fit tight against their respective retaining means 80 and 134, they are held in position by the halfnuts 168'. The advantage to be gained by this split conknob 52 and shaft 164 are rotated both cams are moved axially along the shaft, but one leads the other.

Referring now to the operation of the apparatus of the invention, energization of motor 24 causes rotation of its output shaft 26, gears 28 and 30 and shaft 16. Rotation of this latter shaft produces the desired rotation of cylindrical drum 12 and also causes bevel gear 112 to drive spur gear 126 in a one-to-one relationship by means of bevel gear 114, shaft 116, and spur gears 118 and 124. The rotation of this latter gear causes shaft 128 to rotate and carry with it cam member 130 which is keyed thereto. Ignoring for the moment the question of the positioning of cam member 130 axially of shaft 128, the cam follower rack 138 will be reciprocally translated through a selected amplitude by means of the Archimedean spiral configuration of the cam surface and in a manner which has a linear relationship with the rotation of shaft 128, and hence with the rotation of drum 12.

Pinion gear 144 follows the motion of rack 138, and translates the linear motion of the rack into a rotary motion of a corresponding amplitude. This rotary motion is transferred by means of shaft 146 to the differential mechanism 122, the two transverse forks of the shafts serving to transmit this metered motion to the bevel gear 152 in conjunction with that transmitted by bevel gear 120 which is secured to the rotary input shaft 116. The

differential output is taken from gear 152 through hollow shaft-154 and bevel gears 156, 158, 160 and 162 to the shaft 14 of cylindrical drum 10.

With the two drums in some suitable fiducial position, the cam member is preferably positioned rotationally so as to present the portion of shortest radius for the selected transverse section to the cam follower rack 138. As the drum 12 is rotated, cam 130 is similarly rotated and the rack is driven to the left in Fig. 3 an amount proportional to the cam portion of greatest radius for the selected transverse section. Where this greatest radius produces a rotation of shaft input rotation from shaft 16, a one-to-one ratio is effected and neither enlargement nor reduction of the original copy is achieved. If the cam 130 were to be moved from such an axial position on shaft 128 to anotherposition closer to gear 126, then the greatest radius of the newly selected transverse section of the cam would be even greater than before, and cam follower rack 138 would transmit a greater amplitude of movement to pinion 144 and the subsequent gearing leading to shaft 14 of drum 10. In this case, drum 10 would be rotated an amount greater than that of drum 12, and since drum 10 has been designated as the copy support and drum 12 the recording drum, the end result will be a reduction in size between the original matter on drum 10 and the recording or engraving on drum 12. Conversely, if the earn 130 is moved from the first selected axial position to one fanther away from gear 126, the recording on drum 12 will constitute an enlargement of the image supported on drum 10. This, of course, assumes that the diameters of drums 10 and 12 are equal. The utilization of a plurality of drums of different diameters would have the effect of extending the range of enlargement or reduction of the apparatus.

The rotation of shaft 16 by means of motor 24 and the associated gearing also causes rotation of worm 32 and the adjacent worm gear 34. By means of another worm 36 and gear 38, drive wheel 40 is caused to rotate at a speed relatively slow as compared to that of shaft 16. As wheel 40 is thus rotated, belt 42 pulls output transducer assembly 20 along on rods 22 in order that the transducer may scan the length of the drum 12. The travel of belt 42 also causes rotation of wheel 44, which rotation is 14 which is equal to the to those skilled in the art that the invention transmitted on a one-to-one basis to shaft 72 by means of gears 58 and 60, shaft 62, and gears 66, 74 and 70. As in the case of the previously discussed variable-ratio drive between the two rotary drums, the rotation of the cam member (here, cam 76) causes metered movement of the cam follower rack (85), the associated pinion and subsequent gearing and differential. Wheel 43, and thus belt 54, are supplied with a metered motion which is under the control of the cam 76. For that position of the cam 76 axial of shaft 72 where the movement applied to belt 54 equals that of the input belt 4-2, the two trans ducer assemblies are moved through the same distances and neither enlargement nor reduction of the original copy material is effected. If cam 7 6 were to be moved axially of shaft 72 to a position closer to gear 70 that before, then the greatest radius of the newly selected transverse cam section would be even greater than before, and cam follower rack 85 would be given a greater throw. This greater motion is transmitted through the pinion and subsequent gearing as before to cause a greater amplitude of travel of belt 54, resulting in a reduction of the original copy as seen at the output. Conversely, if cam 76 were to be moved axially of shaft '72 to a position farther away from gear 70 than the first'selected position, the motion transmitted to rack 85 and belt 54 is less than before, and enlargement of the copy matter is the result.

If the two cam members 76 and 130 were to be positioned at different axial points along shaft 164 as discussed in connection with Fig. 6, then the same operation in enlargement or reduction as above would obtain with the exception that the enlargement or reduction in one direction on the copy material would be greater than that in a mutually orthogonal direction. For example, for certain types of art work, it may prove desirable to elongate in one direction the image carried by the original copy. By positioning brackets 84 (Fig. 6) at different axial points on shaft 164, such distortion may be introduced in controllable amounts.

The invention has been described above in considerable detail, and particularly with reference to its application to engraving or copying machines which utilize photoelectric pick-means for sensing the image information in the copy material. However, it will be apparent is also applicable to machines of this general nature which employ mechanical or other means as the sensing element. Further, the output transducer may suitably be a hot-wire engraver for plastic sheets, a light valve for photographic recording or any other of several well known recording devices. Hence, the invention is not to be considered to be limited to the particular details given, nor to the specific application to which reference has been made during the description of theapparatus, except insofar as may be required by the scope of the appended claims.

What is claimed is:

1. An apparatus for the photoelectric reproduction of images, comprising a pair of cylindrical drums mounted for rotation about their respective axes, means on one of said drums for releasably securing thereto image-bearing sheet material, means on the other of said drums for releasably securing thereto recording sheet material upon which it is desired to reproduce such images, photoelectric pick-up transducer means mounted adjacent said one drum for sliding motion parallel to the axis thereof and adapted thereby to scan such image-bearing sheet material, output transducer means electrically connected to said photoelectric transducer means and mounted adjacent said other drum for sliding motion parallel to the axis thereof, means for rotating a first of said drums, means for moving the transducer means adjacent said first drum in timed relation to the rotation thereof, a first variable-ratio drive means interconnecting the second of said drums and said means for rotating said first drum, a variable-ratio drive means inte'connecting the transducer means adjacent said second drum and said means for moving the transducer means adjacent said first drum, and adjustable means for effecting a selected ratio for saidsecond-mentioned drive means; said first drive means including a difierential device for imparting to the second of said drums a rotational speed which changes, during each rotation thereof, between two discrete values whose time-average equals the speed of rotation of said first drum.

2. Apparatus in accordance with claim 1, including means for variably adjusting the value of at least one of the said discrete values of rotational speed of the second of said drums.

3. An apparatus for the photoelectric reproduction of images, comprising a pair of cylindrical drums mounted for rotation about their respective axes, means on one of said drums for releasably securing thereto image-bearing sheet material, means on the other of said drums for releasably securing thereto recording sheet material upon which it is desired to reproduce such images, photoelectric pick-up transducer means mounted adjacent said one drum for sliding motion parallel to the axi thereof and adapted thereby to scan such image-bearing sheet material, output transducer means electrically connected to said photoelectric transducer means and mounted adjacent said other drum for sliding motion parallel to the axis thereof, an axle for a first of said drums, motive means for rotating said axle, an endless belt member passing over and extending between a pair of rotary wheel members, one of the reaches of said belt member being substantially parallel to said axle and secured to the transducer means adjacent said first drum, gearing connected between said axle and one of said wheels to transmit rotary motion thereto upon rotation of said axle, a second pair of rotary wheels, a second endless belt member passing over and extending between said second pair of wheels, an axle for the second of said drums, one of the reaches of said second belt member being substantially parallel to the axle of said second drum and secured to the transducer means adjacent said second drum, means connecting the axles of said first and second drums for causing rotation of the latter in timed relation with that of the former, and variable-ratio drive means interconnecting said second wheel associated with said first endless belt member and a first of the said wheels associated with said second endless belt member; said variable-ratio drive means including a first rotary input member of a difierential mechanism and a rotary conical cam member both driven by gearing connected to said second wheel associated with said first endless belt member, a reciprocally-mounted spring-loaded toothed rack member engaging the cam surface of said cam member, a pinion gear engaging the toothed portion of said rack member and secured to a second rotary input member of said difierential mechanism, an output member of said differential mechanism connected by gearing means to one of said pair of wheels associated with said second endless belt member, and means for effecting linear translation of said cam member along its axis of rotation to selected positions corresponding to desired ratios of operation for said variable ratio drive means.

4. An apparatus for the photoelectric reproduction of images, comprising a pair of cylindrical drums mounted for rotation about their respective axes, means on one of said drums for releasably securing thereto image-bearing sheet material, means on the other of said drums for releasably securing thereto recording sheet material upon which it is desired to reproduce such images, photoelectric pick-up transducer means mounted adjacent said one drum for sliding motion parallel to the axis thereof and adapted thereby to scan such image-bearing sheet material, output transducer means electrically connected to said photoelectric transducer means and mounted adjacent said other drum for sliding motion parallel to the axis thereof, an axle for a first of said drums, motive means for rotating said axle, an endless belt member passing over and extending between a pair of rotary wheel members, one of the reaches of said belt member being substantially parallel to said axle and secured to the transducer means adjacent said first drum, gearing connected between said axle and one of said wheels to transmit rotary motion thereto upon rotation of said axle, a second pair of rotary wheels, a second endless belt member passing over and extending between said second pair of wheels, an axle for the second of said drums, one of the reaches of said second belt member being substantially parallel to the axle of said second drum and secured to the transducer means adjacent said second drum, drive means interconnecting said second wheel associated with said first endless belt member and a first of the said wheels associated with said second endless belt member for causing rotation of the latter in timed relation with that of the former, and variable-ratio drive means interconnecting the axles of said first and second drums; said variable-ratio drive means including a first rotary input member of a'difierential mechanism and a rotary conical cam member both driven by gearing connected to said axle of said first drum, a reciprocally-mounted springloaded toothed rack member engaging the cam surface of said cam member, a pinion gear engaging the toothed portion of said rack member and secured to a second rotary input member of said differential mechanism, an output member of said differential mechanism connected by gearing mean-s to means for effecting linear translation of said cam member along its axis of rotation to selected positions corresponding to desired ratios of operation for said variable-ratio drive means.

5. An apparatus for the photoelectric reproduction of images, comprising a pair of cylindrical drums mounted for rotation about their respective axes, means on one of said drums for releasably securing thereto image-bearing sheet material, means on the other of said drums for releasably securing thereto recording sheet material upon which it is desired to reproduce such images, photoelectric pick-up transducer means mounted adjacent said one drum for sliding motion parallel to the axis thereof and adapted thereby to scan such image-bearing sheet material, output transducer means electrically connected to said extending between said second pair of wheels, an axle for the second of said drums, one of the reaches of said second belt member being substantially parallel to the axle of said second drum and secured to the transducer means adjacent said second drum, a first variable-ratio drive means interconnecting the axles of said first and seovariable-ratio drive means including a first rotary input member of a diiferential mechanism and a rotary conical cam member both driven by gearing connected to said axle of said first drum, a reciprocally-mounted spring-loaded toothed rack member engaging the cam surface of said cam member, a pinon gearengaging the toothed portionof said rack member andsecured to a second rotary input member of said differential mechanism, an output member of said difierential mechanism connected by gearing means to said axle of said second drum, and means for effecting linear translation of said cam member along its axis of rotation to selected positions corresponding to desired ratios of operation for said first variable-ratio drive means, and said second variable-ratio drive means including a first mechanism and a rotary conical cam member both driven by gearing connected to said second wheel associated said axle of said second drum, and

photoelectric transducer means and mounted adjacent saidv other drum for sliding motion parallel to the axis thereof, an axle for a first of said drums, ing said axle, an endless belt member passing overv and extending between a pair of rotary wheel members, one

of the reaches 'of said belt member being substantially parallel to said axle and secured to the transducer means adjacent said first drum, gearing connected between said 7 axle and one of said wheels thereto upon rotation of said to transmit rotary motion axle, a second pair of rotary wheels, at second endless belt member passing over and motive means for r'otatwith said first endless belt member, a reciprocallymounted spring-loaded toothed rack member engaging the cam surface of said cam member, a pinon gear engaging the toothed portion of said rack member and secured to a second rotary input member of said dilferential mecha-S along its axis of rotation to selected positions corresponding to desired ratios of operation for said second variableratio drive means. 1

6. An apparatus for the photoelectric reproduction of images in accordance with claim 5, and, control means common to both said first and second variable-ratio drive means and connected to each of said means for efiecting linear translation of said cam members.

References Cited in the file of this patent v f UNITED STATES PATENTS rotary input member of a differential nism, an output member of said differential mechanism" I connected by gearing means to one of said pair of wheels, associated with said second endless belt member, and means for etfecting linear translation of said cam member Great Britain Nov. 21, 1956 f 3 

